A rotary hearth furnace is a movable hearth furnace for heating and reducing metal oxides such as iron ore or the wastes of iron making, and a rotary hearth furnace, the hearth of which is a horizontal surface and rotates, is known from Japanese Examined Patent Publication (Kokoku) No. 45-19569, and so forth.
The raw-material processed inside this rotary hearth furnace is, in advance, agglomerated and is charged into the rotary hearth by a charging device provided at an upper part of the furnace. Because an outer peripheral portion of the rotary hearth has a greater area than its inner peripheral portion, however, contrivances are required so as to uniformly disperse the raw materials on the entire surface of the rotary hearth. Therefore, a vibration conveyor and a swivel conveyor have been used in the past for this uniform dispersion charging device.
Japanese Unexamined Patent Publication (Kokai) No. 11-293317, for example, discloses a mechanism for charging a pellet (hereinafter called “raw material”) into a rotary hearth furnace, having the construction in which a plurality of screens for dividedly guiding the pellets is arranged in a trough of a vibration conveyor for charging the pellet to the rotary hearth furnace and uniformly charges the pellets into the rotary hearth furnace by adjusting openings of passages partitioned by these screens.
Japanese Unexamined Patent Publication (Kokai) No. 11-337265 discloses a mechanism for uniformly charging the pellets into the rotary hearth furnace by adjusting a swivel speed in accordance with a position of a pivot of the swivel conveyor.
However, the agglomerated raw material has various properties such as low strength, brittleness, easy adhesion, etc, depending of the condition of the raw material, formation method and water content. Therefore, the conventional method or the method using the vibration conveyor, for example, is not able to satisfy the charging function itself because it invites dusting, deformation and mutual adhesion, by the application of vibration to the agglomerated raw material.
The swivel conveyor has theoretically only a function of charging the raw material onto the swivel orbit and is a system that cannot uniformly disperse and charge the pellet.